/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.rpc;

import org.apache.thrift.TConfiguration;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;
import org.apache.thrift.transport.TTransportFactory;
import org.apache.thrift.transport.layered.TFramedTransport;

// https://github.com/apache/thrift/blob/master/doc/specs/thrift-rpc.md
public class TElasticFramedTransport extends TTransport {

    public static class Factory extends TTransportFactory {

        /**
         * It is used to prevent the size of the parsing package from being too large and allocating the
         * buffer will cause oom. Therefore, the maximum length of the requested memory is limited when
         * reading.
         */
        protected final int thriftMaxFrameSize;

        /**
         * The capacity of the underlying buffer is allowed to exceed thriftDefaultBufferSize, but if
         * adjacent requests all have sizes smaller than thriftDefaultBufferSize, the underlying buffer
         * will be shrunk beneath thriftDefaultBufferSize. The shrinking is limited at most once per
         * minute to reduce overhead when thriftDefaultBufferSize is set unreasonably or the workload
         * naturally contains both ver large and very small requests.
         */
        protected final int thriftDefaultBufferSize;

        public Factory() {
            this(RpcUtils.THRIFT_DEFAULT_BUF_CAPACITY, RpcUtils.THRIFT_FRAME_MAX_SIZE);
        }

        public Factory(int thriftDefaultBufferSize, int thriftMaxFrameSize) {
            this.thriftDefaultBufferSize = thriftDefaultBufferSize;
            this.thriftMaxFrameSize = thriftMaxFrameSize;
        }

        @Override
        public TTransport getTransport(TTransport trans) {
            return new TElasticFramedTransport(trans, thriftDefaultBufferSize, thriftMaxFrameSize);
        }
    }

    public TElasticFramedTransport(TTransport underlying) {
        this(underlying, RpcUtils.THRIFT_DEFAULT_BUF_CAPACITY, RpcUtils.THRIFT_FRAME_MAX_SIZE);
    }

    public TElasticFramedTransport(
            TTransport underlying, int thriftDefaultBufferSize, int thriftMaxFrameSize) {
        this.underlying = underlying;
        this.thriftDefaultBufferSize = thriftDefaultBufferSize;
        this.thriftMaxFrameSize = thriftMaxFrameSize;
        readBuffer = new AutoScalingBufferReadTransport(thriftDefaultBufferSize);
        writeBuffer = new AutoScalingBufferWriteTransport(thriftDefaultBufferSize);
    }

    protected final int thriftDefaultBufferSize;
    protected final int thriftMaxFrameSize;

    protected final TTransport underlying;
    protected AutoScalingBufferReadTransport readBuffer;
    protected AutoScalingBufferWriteTransport writeBuffer;
    protected final byte[] i32buf = new byte[4];

    @Override
    public boolean isOpen() {
        return underlying.isOpen();
    }

    @Override
    public void open() throws TTransportException {
        underlying.open();
    }

    @Override
    public void close() {
        underlying.close();
    }

    @Override
    public int read(byte[] buf, int off, int len) throws TTransportException {
        int got = readBuffer.read(buf, off, len);
        if (got > 0) {
            return got;
        }

        // Read another frame of data
        readFrame();
        return readBuffer.read(buf, off, len);
    }

    protected void readFrame() throws TTransportException {
        underlying.readAll(i32buf, 0, 4);
        int size = TFramedTransport.decodeFrameSize(i32buf);

        if (size < 0) {
            close();
            throw new TTransportException(
                    TTransportException.CORRUPTED_DATA, "Read a negative frame size (" + size + ")!");
        }

        if (size > thriftMaxFrameSize) {
            close();
            throw new TTransportException(
                    TTransportException.CORRUPTED_DATA,
                    "Frame size (" + size + ") larger than protect max size (" + thriftMaxFrameSize + ")!");
        }
        readBuffer.fill(underlying, size);
    }

    @Override
    public void flush() throws TTransportException {
        int length = writeBuffer.getPos();
        TFramedTransport.encodeFrameSize(length, i32buf);
        underlying.write(i32buf, 0, 4);
        underlying.write(writeBuffer.getBuffer(), 0, length);
        writeBuffer.reset();
        if (length > thriftDefaultBufferSize) {
            writeBuffer.resizeIfNecessary(thriftDefaultBufferSize);
        }
        underlying.flush();
    }

    @Override
    public TConfiguration getConfiguration() {
        return underlying.getConfiguration();
    }

    @Override
    public void updateKnownMessageSize(long size) throws TTransportException {
        // do nothing now.
    }

    @Override
    public void checkReadBytesAvailable(long numBytes) throws TTransportException {
        // do nothing now.
        // here we can do some checkm, e.g., see whether the memory is enough.
    }

    @Override
    public void write(byte[] buf, int off, int len) {
        writeBuffer.write(buf, off, len);
    }

    public TTransport getSocket() {
        return underlying;
    }
}
